Plate-type heat exchanger



May 3, 1966 A. HUET PLATE-TYPE HEAT EXCHANGER Filed Feb. 18, 1963 United States Patent 3,249,155 PLATE-TYPE HEAT EXCHANGER Andre Huet, 48 Ave. du President Wilson, Paris, France Filed Feb. 18, 1963, Ser. No. 259,345 Claims priority, application France, Mar. 23, 1962, 892,019, Patent 1,325,843 7 Claims. (Cl. 165166) It is known that for heat exchange between certain fluids, in particular in'the case of air heaters, plate type heat exchangers may be employed of the type in which a nest of parallel plates provides parallel adjacent passages, the two fluids passing through respective alternate passages and exchanging heat through the walls of the plates which separate the two fluids.

The object of the present invention is an improvement of thi-s'type of heat exchanger, according to which improvement there are provided grooves or small protrusions over a part of or over the entire surface of the plates, which grooves preferably extend in the general direction of the flow of fluid circulating along the plates, or may of the fluid flow passages, which variations lead to changes of pressure and direction of flow of the fluids, these being advantageous for the exchange of heat between the fluids.

In the case where one of the fluids which circulates in the exchanger is a dirty fluid as may be, for example, the heating fluid employed in air heaters for boilers, those sides of the plates which face the passages through which this dirty fluid flows are not grooved and the grooves or protrusions then are only provided on those sides of the plates which face the passages traversed by the non-dirty fluid, in this case air which it is desired to heat.

The following description, illustrated by the attached drawings, given by way of example, will facilitate understanding how the invention may be put into effect.

FIG. 1 is a schematic cross-section of a heat exchanger having parallel corrugated plates, and suitable for heating air for a boiler.

FIG. 2 shows in perspective a partial view of the plates of the heat exchanger shown in FIG. 1 and which are in accordance with the present invention.

FIG. 3 is a transverse cross-section of a plate of the heat exchanger shown in FIG. 2.

FIGS. 4a and 4b are plan views of plates of heat exchangers showing some variants of the fonrnof the grooves which can be employed on the surface of the .plates.

FIG. 5 is a perspective view of two superimposed heat exchanger plates, in which plates the grooves extend in two respective directions, and are inclined with respect to the direction of flow of the fluid between the plates.

FIG. 1 shows, in a schematic manner, and in crosssection, an air heater constituted by a nest of parallel plates a, corrugated in a non-symmetrical manner, and providing between them passages b and c. The passages c are traversed by heating fluid, for example gas coming out of the boiler furnace and flowing in the direction of the arrows A inside a housing h. In the passages b provided between the :plates, which passages alternate with the passage-s 0, air to be heated circulates in the direction of arrows B, and which enters perpendicularly to the plane of the figure, at the upper part of the passages and leaves, also perpendicularly to the plane of the figure, at the lower part of the said passages.

"Ice

In the embodiment shown in FIG. 1, the corrugation of the plates is not symmetrical, that is to say, each corrugation is formed of a first portion, short in length and steeply sloped, followed by a second portion, longer and less steeply sloped than the first portion. The plates are so arranged with respect to each other that there is a restriction of the passage b or 0 between adjacent plates, in the neighbourhood of the apex of a corrugation.

According to the invention, the plates a are, either over one of their surfaces, or over both surfaces, or over a part only of their surface, provided with grooves, or small protrusions, preferably orientated in the general direction of the flow of the fluid.

In the case of an air heater, such as is shown in FIG. 1 the fluid which circulates in passages c is a dirty heating fluid (coming from a boiler furnace) and preferably the surfaces of the plates a which face the passages c are left smooth. On the other hand, air circulating through the passages b, in the direction of the arrows B, is clean, and grooves are provided on the surfaces of the plates a which face the passages b. This arrangement is shown in perspective in FIG. 2, which shows a part of the heat exchanger shown in FIG. 1, and in which grooves d, arranged parallel with the direction of flow of the fluids, are provided on the surfaces of the plates a which face the passages b, in which circulates clean hot air.

F'IG.- 3 shows in cross-section the parallel grooves d provided on the plate a.

It is not absolutely necessary that these grooves shall extend in the direction of the flow of the fluid, and it can be arranged, as shown schematically in FIGS. 4a and 4b, that for the flow in the direction of arrows B, the grooves may extend perpendicularly to this direction, as shown at e (FIG. 4a). These grooves may also be of a herringbone pattern as shown at 1 (FIG. 4b).

. In certain cases, the grooves g can, as seen in FIG. 5, be slightly inclined to the direction of fluid flow B. For one of the plates a grooves'g are inclined in one direction with respect to the direction B, while for the plate a which is parallel to the plate a, grooves g, shown in chain-dotted lines in FIG. 5 are inclined in an opposite direction with respect to the direction B.

The degree of depth or height of the grooves or ridges is of the order of l millimetre to A of a millimetre. The plates may be closer to each other than shown in FIG. 1, so that the passages for the fluids which exchange heat, may have a width of the order of 1 millimetre or even of a millimetre.

It may also be arranged that the ridges, grooves or other protrusions provided on the plates are closer or more distant from each other depending on their position on the plate, that is to say according to whether they are closer to or more distance from the entry or exit of the fluid which is to circulate in the passage between two plates. The distance between the ridges, grooves or other protrusions may also be affected by their position on the plate in relation to the corrugations, which may be provided in the plates. For example, the grooves may be situated in the neighbourhood of the restrictions of the passage cross-section, or to the contrary, in the divergent parts of the passages.

Advantages of the features which have been described reside in the fact that, flrstly, the plate surface available for heat exchange is increased, and in principle doubled, which has been found to improve the coeflicient of heat exchange from 1.5 to 2 times, depending on whether the plate is grooved on one or both of its surfaces. Moreover, the obstruction to the flow of fluid which circulates in the passages caused by the grooves, breaks up the fluid boundary layer which, as is known, tends to adhere to the plate and is. detrimental to the satisfactory heat exchange. Finally, the protrusions provided on the plates also have the effect of stiffening them, and the result is that it is possible to employ thinner plates to resist higher pressures. It is also possible to increase the rigidity of the plates and thus contrary to normal practice in plate type heat exchanger construction, the supporting ties arranged between the plates may be dispensed 'With or reduced in number. The flow of fluids between the plates is thereby facilitated, and the pressure losses suffered by the circulating fluids inside the exchanger are diminished.

The ridges, grooves or protrusions may be provided during hot or cold rolling of the material for the plates, by employing of one or two roll cylinders upon which have been machined the negatives of the impressions which it is desired to obtain. The patterns also may be obtained by machining or by pressing.

It will be understood that modifications of details can be made, without exceeding the scope of the invention.

What I claim is:

1. A plate-type heat exchanger comprising a housing, a plurality of spaced plates arranged in said housing and defining passages between adjacent pairs of said plates, alternate ones of said passages constituting first fluid-flow passages and the intervening passages constituting second fluid-flow passages, a first fluid inlet in said housing in communication with one end of each of said first passages, a first fluid outlet in said housing in communication with the other end of each of said first passages, a second fiiud inlet in said housing in communication with one end of each of said second passages, a second fluid outlet in said housing in communication with the other end of each of said second passages, and a plurality of closely adjacent small grooves with intervening ridges provided in both of the opposing surfaces of each pair of plates defining each of said flrst-fluid-low passages to provide said plates with striated surfaces, the ridges of each of said surfaces being spaced from the opposing surface of the other plate of each said pair of plates defining each of said first flow passages and the crosssectional area of said grooves being less than the crosssectional area of said plates.

2. A plate-type heat exchanger according to claim 1, in which the grooves provided in each such opposing surface extend substantially in the direction of fluid flow through said first passages.

3. A plate-type heat exchanger according to claim 1, in which the grooves provided in one such opposing surface extend obliquely to the direction of fluid flow through said first passages, and the grooves provided in the other such opposing surface extend obliquely in an opposite respect to the direction of fluid flow through said first passages.

4.?A plate-type heat exchanger according to claim 1, in which the clear space between each pair of said opposing surfaces is substantiallythe same as the depth of the grooves provided in each such opposing surface.

5. A plate-type heat exchanger according to claim 1, in which the opposing surfaces of each pair of said plates defining said second fluid-flow passages are smooth and ungrooved.

6. A plant-type heat exchanger according to claim 1, in which said grooves have a depth of the order of one millimeter.

7. A plate-type heat exchanger according to claim 6, in which the clear space between successive plates is of the order of one millimeter.

References-Cited by the Examiner UNITED STATES PATENTS 1,662,870 3/1928 Stancliffe 165-466 3,136,037 6/1964 Solnick et a1 165170 FOREIGN PATENTS 199,679 9/1958 Austria. 552,477 11/ 1956 Belgium. 845,942 5/1939 France. 144,776 4/1954 Sweden.

ROBERT A. OLEARY, Primary Examiner.

CHARLES SUKALO, FREDERICK L. MATTESON,

JR., Examiners.

S. W. MILLARD, T.W. STREULE, Assistant Examiners. 

1. A PLATE-TYPE HEAT EXCHANGER COMPRISING A HOUSING, A PLURALITY OF SPACED PLATES ARRANGED IN SAID HOUSING AND DEFINING PASSAGES BETWEEN ADJACENT PAIRS OF SAID PLATES, ALTERNATE ONES OF SAID PASSAGES CONSTITUTING FIRST FLUID-FLOW PASSAGES AND THE INTERVENING PASSAGES CONSTITUTING SECOND FLUID-FLOW PASSAGES, A FIRST FLUID INLET IN SAID HOUSING IN COMMUNICATION WITH ONE END OF EACH OF SAID FIRST PASSAGES, A FIRST FLUID OUTLET IN SAID HOUSING IN COMMUNICATION WITH THE OTHER END OF EACH OF SAID FIRST PASSAGES, A SECOND FLUID INLET IN SAID HOUSING IN COMMUNICATION WITH ONE END OF EACH OF SAID SECOND PASSAGES, A SECOND FLUID OUTLET IN SAID HOUSING IN COMMUNICATION WITH THE OTHER END OF EACH OF SAID SECOND PASSAGES, AND A PLURALITY OF CLOSELY ADJACENT SMALL GROOVES WITH INTERVENING RIDGES PROVIDED IN BOTH OF THE OPPOSING SURFACES OF EACH PAIR OF PLATES DEFINING EACH OF SAID FIRST-FLUID-FLOW PASSAGES TO PRO- 